Fundamental Study on Injector Flow Characteristics of Self-Pressurizing Fluid for Small Rocket Engines
Fundamental Study on Injector Flow Characteristics of Self-Pressurizing Fluid for Small Rocket Engines
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小型火箭发动机自增压流体喷油器流动特性基础研究
DOI：
10.1115/1.4048688
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Kugo Okada and Ryoji Imai
中科院分区：
文献类型：
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作者：
Kazuki Yasuda;Daisuke Nakata;Masaharu Uchiumi;Kugo Okada and Ryoji Imai
一氧化二氮是一种适用于火箭发动机的推进剂，由于其高的饱和蒸汽压，可以实现自增压，因此在各国得到了广泛的应用。由于一氧化二氮在储罐内处于汽液平衡状态，在进料线上容易形成气液两相流。由于准确估计火箭发动机的性能需要对推进剂流动特性进行评估，因此本文报道了混合动力火箭发动机在冷流试验、低背压热发射试验和高背压热发射试验三种情况下进行的试验。考虑到过冷度，一氧化二氮在喷嘴上游流动中可能处于非稳态过热状态。通过对各试验条件下喷油器压力比的比较，发现在冷流试验和低背压点火试验中，喷油器内形成了临界两相流。在高背压热射试验中，喷油器流动可能会被堵塞，但燃烧室压力和推力有较大的波动。根据FFT分析结果，这些振荡是由嗡嗡声和声学振荡引起的。根据这些实验结果，提出了当燃烧室压力因燃烧不稳定性而波动时，可能会影响喷油器的流动特性和临界两相流。
Nitrous oxide is a suitable propellant for rocket engines and has been widely used in various countries, given its high saturated vapor pressure, which enables self-pressurization. Because nitrous oxide is in a state of vapor–liquid equilibrium in tanks, it is easy to form a gas–liquid two-phase flow by cavitation in feed line. Since accurately estimating the performance of rocket engines requires evaluating the characteristics of propellant flows, tests reported in this paper were conducted using hybrid rocket engines under three conditions: cold flow test, hot firing test at low back pressure, and hot firing test at high back pressure. With consideration to the subcooling degrees, nitrous oxide may be in an unsteady superheated state in the upstream flow of the injector. In a comparison of the pressure ratios between the injector in each test condition, it is observed that a critical two-phase flow was formed in the injector in the cold flow test and in the low backpressure firing test. In the high backpressure hot firing test, the injector flow may be choked, but the large oscillations were observed in chamber pressure and thrust. According to the FFT analysis results, these oscillations were caused by chugging and acoustic oscillation. In light of these experimental results, it is suggested that when the chamber pressure fluctuates due to combustion instability such as chugging and acoustic oscillation, it may affect the injector flow characteristics and the critical two-phase flow.